Warning: The following contains spoilers from Detective Comics #1021 by Peter J. Tomasi, Brad Walker, Andrew Hennessy, Brad Anderson, and Rob Leigh, on sale now.
By any measure, Batman has a very impressive resume. Considered by many to be the world’s greatest detective, Batman is arguably DC's best tactical genius, and he's in peak physical condition. Even though he doesn't have any physical powers, Batman has a superior intellect that places him in the upper echelon of the heroes comprising the DC Universe.
Underneath it all, however, Batman is still human. And because he is human, he is privy to making mistakes, particularly when it comes to people he considers to be friends. And in Detective Comics #1021, Batman is investigating a string of murders that appears to be connected to Two-Face, who used to be his childhood pal Harvey Dent.
Because of their childhood friendship and the partnership they had as Gotham's vigilante and district attorney, Dent knows Batman's secret identity, even if his lesser half doesn't. While Batman was driving the Batmobile, Dent stopped Batman in his tracks by addressing the Dark Knight by his real name, Bruce.
When Batman stops, Dent desperately asks him for help in controlling his murderous alter ego from continuing his murderous rampage. Batman says that the only way to help his friend is to take him back to Arkham Asylum, and he tells Dent to get in the car.
Related: Detective Comics Reveals an Unknown Link Between Joker and Two-Face
While in the Batmobile, Dent begins to talk about how his other side is trying to take over and waiting for the perfect opportunity to strike. Batman responds by reminding his friend that “Harvey Dent is stronger than Two-Face” and encourages him to keep fighting. Batman stops at the Gotham Courthouse to follow up on his investigation into what Two-Face is up to. He leaves Dent cuffed in the Batmobile while he emits an electromagnetic pulse before infiltrating the building.
While confined in the Batmobile, Dent pounds away from the inside of the car, angry that he has been left behind and insisting that he can control Two-Face. He sets off an explosion that breaks the cuffs and bashes his head against the roof of the car, knocking him for enough of a loop that his Two-Face personality is able to come to the forefront. Two-Face escapes from the damaged vehicle and makes his way into the courthouse. The deranged villain manages to sneak up on Batman just as the detective has discovered a cult of Two-Face followers. While Batman is still stunned by his discovery, Two-Face pulls a gun on the hero and unloads several shots, leaving Batman a bloodied, smoking mess on the floor.
While Batman is usually one of DC's best decision-makers, Dent appealed to Batman's past and his humanity by addressing him as Bruce. That brought Batman's guard down just enough that he let Two-Face into the Batmobile. Even if he locked him in there, the Dark Knight still left one of his most dangerous villains in one of DC's most powerful and potentially destructive vehicles unsupervised.
Perhaps blinded by his own belief in what's left of his old friend, Batman made the rare mistake of trusting that Deny could control the Two-Face persona long enough for the detective to get his investigation done. However, he realized that Two-Face was much stronger than he thought, and the results of that misplaced trust were disastrous.